Gold is extensively used in industrial applications both for decorative purposes and in more utilitarian application. Gold is often used both in solid form and in the form of thin surface films in jewelry such as watches, rings, pins, chains, etc. Gold is also used extensively in electrical devices as a contact metal, electrical conduction paths and sometimes as a heat sink material.
Gold is often applied to surfaces by chemical means such a electroplating, electroless plating, displacement plating, etc. Such processes require that the gold be in the form of an ion soluble in a solvent such as water; often in the form of a cyanide complex ion such as Au(CN).sub.2.sup.-. In such procedures, gold plating solution is rinsed from the piece being plated. The resulting rinse water contains gold in a highly diluted state. Recovery of this gold is highly advantageous economically.
Much of the interest in this particular area arises because of the increasing use and importance of gold in the electronics industry and the high and variable price of gold. For example, in some gold electroplating processes, extremely high rates are used and large amounts of product are electroplated per unit time. Such a process is described in a number of references including, U.S. Pat. No. 4,153,523 issued to D. E. Koontz and D. R. Turner on May 8, 1979; U.S. Pat. No. 4,230,538 issued to D. R. Turner on Oct. 28, 1980 and U.S. Pat. No. 4,278,520 issued to D. R. Turner on July 4, 1981. Particularly significant in these references is the large amount of rinse water used to remove gold plating solution from the articles being gold plated.
A particularly efficient procedure for removing a soluble gold in aqueous solutions such as rinse water, spent plating baths, drag-out solutions, etc., is the use of exchange resins. Typically, the soluble gold is in the form of potassium gold cyanide and this compound is absorbed on an anion-exchange resin. To recover the gold, the resin is often dried and then incinerated. The incineration method often resulted in losses of precious metals and loss of the exchange resin. It is highly desirable to have a procedure which would lead to recovery of essentially all of the gold and be non-destructive to the resin. Also, incineration of the resin leads to pollution problems which are desirable to avoid. An extractive process for removing gold from resins is described by F. H. Burstall et al in Industrial and Engineering Chemistry, Vol. 45, page 1648 (1953).